1. Field of the Invention
The present invention relates to enhancing reception of wireless signals. More specifically, it relates to selective mitigation of interference.
2. Brief Description of the Related Art
Wireless devices such as cell phones and radios operate in the face of ever increasing interference, be it inadvertent or intentional, which reduces or eliminates the link margin required for the reception of voice or other data. Interference, therefore, reduces the effectiveness of national defense while hastening the time when demand for connectivity exceeds available spectrum capacity.
While the U.S. government is making spectrum at white space frequencies available for consumer use, the interference created by the powerful TV transmissions at adjacent frequencies may limit the quality of service in that spectrum. Clearly, low cost technology providing enhanced quality of service at white space frequencies is desirable.
Radar and related devices use null steering to suppress interference that hinders detection and tracking capabilities. The array antennas that support steering, however, are power hungry, complex and costly, as well as not readily portable. Null steering also requires interference bearing data, which is often not available a priori and is calculated by computationally demanding methods. Clearly, technology that is small enough to integrate into mobile handsets and other radios which can mitigate interference without large arrays of elements and without requiring statistical processing is desirable.
Cosite interference between co-located antennas is a common problem, such as aboard ships where large numbers of antennas must be co-located in limited space, limiting the use of positioning minimize cosite interaction between transmit and receive antennas. As a result, co-located antennas use time sharing to avoid interference reducing the utility of the transmitters and receivers alike. Clearly, technology that can reduce cosite interference without time sharing or other utility limiting approaches is desirable.
Side-lobe blanking has also been described for array antennas, in which temporal segments of signals that include burst interference are excised or ignored. Unfortunately, blanking introduces periods of blindness in reception, rendering an array useless in the face of continuous interference. Clearly, low cost technology that can remove interference without interruption is desirable.
Digital signal processing is proposed to reduce interference such as by using matched filtering and blind source separation. Matched filtering requires a priori information or development of a statistic model of the signal. Unfortunately, waveform data typically is unavailable for dynamic adversarial intentional signals. Blind source separation has been disclosed for isolating desirable signals from interference, which requires substantial amounts of data and processing time. Clearly, technology that can adapt quickly and inexpensively while maintaining effectiveness in the face of dynamic interference is desirable.